U.S. patent application number 15/928229 was filed with the patent office on 2018-09-27 for optical transmitter module, optical module, optical transmission equipment and method of manufacturing thereof.
The applicant listed for this patent is Oclaro Japan, Inc.. Invention is credited to Masahiro EBISU, Yoshihiro NAKAI, Takayuki NAKAJIMA, Shunya YAMAUCHI.
Application Number | 20180278019 15/928229 |
Document ID | / |
Family ID | 63582952 |
Filed Date | 2018-09-27 |
United States Patent
Application |
20180278019 |
Kind Code |
A1 |
YAMAUCHI; Shunya ; et
al. |
September 27, 2018 |
OPTICAL TRANSMITTER MODULE, OPTICAL MODULE, OPTICAL TRANSMISSION
EQUIPMENT AND METHOD OF MANUFACTURING THEREOF
Abstract
An optical transmitter module includes optical semiconductor
devices including a first optical semiconductor device, a
temperature adjustment means for collectively performing
temperature adjustment on the optical semiconductor devices, and a
first thermal resistor that is disposed between the first optical
semiconductor device and the temperature adjustment means, in
which, when the temperature adjustment means is driven, the
temperature of the first optical semiconductor device is higher
than temperatures of other optical semiconductor devices which are
different from the first optical semiconductor device.
Inventors: |
YAMAUCHI; Shunya;
(Sagamihara, JP) ; NAKAI; Yoshihiro; (Sagamihara,
JP) ; NAKAJIMA; Takayuki; (Tokyo, JP) ; EBISU;
Masahiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Oclaro Japan, Inc. |
Sagamihara |
|
JP |
|
|
Family ID: |
63582952 |
Appl. No.: |
15/928229 |
Filed: |
March 22, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S 5/02248 20130101;
H01S 5/068 20130101; H01S 5/02216 20130101; H01S 5/026 20130101;
H01S 5/12 20130101; H01S 5/0612 20130101; H04B 10/40 20130101; H01S
5/02415 20130101; H01S 5/042 20130101; H01S 5/02284 20130101; H01S
5/02236 20130101; H01S 5/02276 20130101; H01S 5/4087 20130101; H01S
5/02484 20130101; H01S 5/0265 20130101 |
International
Class: |
H01S 5/06 20060101
H01S005/06; H01S 5/068 20060101 H01S005/068; H01S 5/022 20060101
H01S005/022; H01S 5/40 20060101 H01S005/40; H01S 5/026 20060101
H01S005/026; H01S 5/12 20060101 H01S005/12; H01S 5/042 20060101
H01S005/042 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2017 |
JP |
2017-059048 |
Claims
1. An optical transmitter module comprising: optical semiconductor
devices including a first optical semiconductor device; a
temperature adjustment means for collectively performing
temperature adjustment on the optical semiconductor devices; and a
first thermal resistor that is disposed between the first optical
semiconductor device and the temperature adjustment means, wherein,
when the temperature adjustment means is driven, the temperature
adjustment means causes the temperature of the first optical
semiconductor device to be higher than temperatures of other
optical semiconductor devices of the optical semiconductor
devices.
2. The optical transmitter module according to claim 1, wherein the
first optical semiconductor device emits one light beam with a
first wavelength which is different from a first predefined
wavelength at a driving temperature which is controlled by the
temperature adjustment means, and wherein, when the temperature
adjustment means is driven, the first thermal resistor shifts a
wavelength of other light beam emitted from the first optical
semiconductor device from the first wavelength closer to the
predefined wavelength.
3. The optical transmitter module according to claim 1, further
comprising: a submount, on which the optical semiconductor devices
are mounted, arranged to thermally connect to the temperature
adjustment means, wherein the first thermal resistor is a first
sub-substrate disposed between the first optical semiconductor
device and the submount in thermal communication with the first
optical semiconductor device and the submount.
4. The optical transmitter module according to claim 3, wherein a
second optical semiconductor device of the optical semiconductor
devices which is different from the first optical semiconductor
device is directly mounted on the submount.
5. The optical transmitter module according to claim 3, further
comprising: a second sub-substrate, disposed between a second
optical semiconductor device of the optical semiconductor devices
and the submount in thermal communication with the second optical
semiconductor device and the submount configured to cause the
temperature of the second optical semiconductor device to be
different from the temperature of the first optical semiconductor
device when the temperature adjustment means is driven, wherein the
second optical semiconductor device is different from the first
optical semiconductor device.
6. The optical transmitter module according to claim 5, wherein the
second optical semiconductor device emits one light beam with a
second wavelength which is different from a second predefined
wavelength in a temperature range controlled by the temperature
adjustment means, and wherein, when the temperature adjustment
means is driven, the second sub-substrate shifts a wavelength of
other light beam emitted from the second optical semiconductor
device from the second wavelength closer to the second predefined
wavelength.
7. The optical transmitter module according to claim 3, further
comprising: sub-substrates, each disposed between a corresponding
optical semiconductor device of the optical semiconductor devices
and the submount in thermal communication with the corresponding
optical semiconductor device and the submount, configured to cause
temperatures of at least two of the optical semiconductor devices
to be different from each other when the temperature adjustment
means is driven.
8. The optical transmitter module according to claim 7, wherein
thicknesses of the sub-substrates are substantially the same.
9. The optical transmitter module according to claim 5, wherein
thermal resistance of the first sub-substrate between the submount
and the first optical semiconductor device is different from
thermal resistance of the second sub-substrate between the submount
and the second optical semiconductor device.
10. The optical transmitter module according to claim 3, wherein
heat conductivity of a material forming the first sub-substrate is
lower than heat conductivity of a material forming the
submount.
11. The optical transmitter module according to claim 1, wherein
the first thermal resistor is a first sub-substrate directly
mounted on the temperature adjustment means, wherein the first
optical semiconductor device is directly mounted on the first
sub-substrate, and wherein a second optical semiconductor device of
the optical semiconductor devices which is different from the first
optical semiconductor device is directly mounted on the temperature
adjustment means.
12. The optical transmitter module according to claim 1, further
comprising: a second sub-substrate, wherein the first thermal
resistor is a first sub-substrate directly mounted on the
temperature adjustment means, wherein the first optical
semiconductor device is directly mounted on the first
sub-substrate, wherein the second sub-substrate is directly mounted
on the temperature adjustment means, wherein the second optical
semiconductor device is directly mounted on the second
sub-substrate, and wherein, when the temperature adjustment means
is driven, the temperature adjustment means causes the temperatures
of the first optical semiconductor device and the second optical
semiconductor device to be different from each other.
13. An optical module comprising: the optical transmitter module
according to claim 1; and an optical receiver module.
14. Optical transmission equipment mounted with the optical module
according to claim 13.
15. A method of manufacturing an optical transmitter module
comprising optical semiconductor devices, a temperature adjustment
means for collectively performing temperature adjustment on the
optical semiconductor devices, and a first thermal resistor,
disposed between a first optical semiconductor device of the
optical semiconductor devices and the temperature adjustment means,
the method comprising: manufacturing the first optical
semiconductor device; measuring an output wavelength of a light
beam emitted from the first optical semiconductor device at a
reference temperature; comparing the output wavelength with a
reference wavelength range corresponding to the first optical
semiconductor device so as to obtain a wavelength difference; and
determining a material and dimensions of the first thermal resistor
on the basis of the wavelength difference.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from Japanese
application JP2017-059048, filed on Mar. 24, 2017, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to an optical transmitter
module provided, an optical module, optical transmission equipment
with a plurality of optical semiconductor devices, and a method for
manufacturing the same, and particularly to temperature adjustment
of the plurality of optical semiconductor devices.
2. Description of the Related Art
[0003] An optical transmitter module provided with a plurality of
optical semiconductor devices is used. For example, an optical
transmitter module further includes a submount and a Peltier
element. The plurality of optical semiconductor devices is disposed
on an upper surface (mounting surface) of the submount, and the
Peltier element is disposed on a lower surface (bottom surface) of
the submount. The plurality of optical semiconductor devices and
the Peltier element are thermally connected to each other via the
submount. A single Peltier element is used to adjust temperatures
of the plurality of optical semiconductor devices.
[0004] JP2013-153136A discloses a transmitter optical subassembly
(TOSA) based on wavelength division multiplexing (WDM), including a
plurality of semiconductor lasers and a Peltier element, and
temperatures are collectively controlled by using a single Peltier
element via the submount.
SUMMARY OF THE INVENTION
[0005] In an optical transmitter module of the related art,
respective temperatures of semiconductor lasers are collectively
adjusted by using a single Peltier element so as to fall within a
desired temperature range. Generally, a large number of
semiconductor lasers are collectively manufactured on a
semiconductor wafer, and then it is tested whether the respective
output wavelengths of light beams emitted from the large number of
semiconductor lasers at a reference temperature (for example,
50.degree. C.) fall within a reference wavelength range. However,
it is hard that the respective output wavelengths of all (or most)
of a large number of semiconductor lasers manufactured on the
semiconductor wafer fall within the reference wavelength range.
Thus, some of the manufactured semiconductor lasers may emit light
beams with the respective output wavelengths which do not fall
within the reference wavelength range. For example, in an optical
transmitter module, where temperatures of semiconductor lasers are
adjusted to a reference temperature (a predefined temperature range
including the reference temperature) by using a Peltier element,
and then subject to a test whether all semiconductor lasers emit
light beams with their respective output wavelengths which fall
within a reference wavelength range. The semiconductor lasers which
pass the test, and are mounted on a submount.
[0006] Generally, an output wavelength of a light beam emitted from
a semiconductor laser depends on temperature of the semiconductor
laser. Therefore, where temperatures of semiconductor lasers are
collectively adjusted by using a Peltier element, the semiconductor
lasers which do not pass the test have to be discarded. As a
result, yield of the semiconductor lasers is reduced, and thus cost
of the semiconductor lasers is increased. In contrast, where
temperatures of the semiconductor lasers are separately adjusted,
even the temperatures of the discarded semiconductor lasers can
also be adjusted to an appropriate temperature, and thus output
wavelengths of the discarded semiconductor lasers can be made to
fall within a predefined wavelength range including the appropriate
temperature. However, in this case, a each of the semiconductor
lasers requires a corresponding temperature adjustment mechanism
such as a Peltier element, and thus drive circuits and the like
driving the respective temperature adjustment mechanisms hinder
miniaturization or achievement of low cost of the optical
transmitter module.
[0007] The present invention has been made in light of the
problems, and an object of the present invention is to provide an
optical transmitter module, an optical module, and an optical
transmission equipment comprising optical semiconductor devices,
and a method of manufacturing of the same, capable of realizing low
cost, miniaturization, and adjustment of the temperature of each of
the optical semiconductor devices.
[0008] (1) In order to solve the problem, according to the present
invention, there is provided an optical transmitter module
including optical semiconductor devices, comprising a first optical
semiconductor device; a temperature adjustment means for
collectively performing temperature adjustment on the optical
semiconductor devices; and a first thermal resistor that is
disposed between the first optical semiconductor device and the
temperature adjustment means, in which, when the temperature
adjustment means is driven, the temperature adjustment means causes
the temperature of the first optical semiconductor device to be
higher than temperatures of other optical semiconductor devices of
the optical semiconductor device.
[0009] (2) In the optical transmitter module according to (1), the
first optical semiconductor device may emit one light beam with a
first wavelength which is different from a first predefined
wavelength at a driving temperature which is controlled by the
temperature adjustment means, and, when the temperature adjustment
means is driven, the first thermal resistor shifts a wavelength of
other light beam emitted from the first optical semiconductor
device from the first wavelength closer to the first predefined
wavelength.
[0010] (3) The optical transmitter module according to (1) or (2)
may further include a submount, on which the optical semiconductor
devices are mounted, arranged to thermally connect to the
temperature adjustment means, and the first thermal resistor may be
a first sub-substrate disposed between the first optical
semiconductor device and the submount in thermal communication with
the first optical semiconductor device and the submount.
[0011] (4) In the optical transmitter module according to (3), a
second optical semiconductor device of the optical semiconductor
devices which is different from the first optical semiconductor
device may be directly mounted on the submount.
[0012] (5) The optical transmitter module according to (3) may
further include a second sub-substrate, disposed between a second
optical semiconductor device and the submount in thermal
communication with the second optical semiconductor device and the
submount, configured to cause the temperature of the second optical
semiconductor device to be different from the temperature of the
first optical semiconductor device when the temperature adjustment
means is driven, and the second optical semiconductor device is
different from the first optical semiconductor device.
[0013] (6) In the optical transmitter module according to (5), the
second optical semiconductor device may emit one light beam with a
second wavelength which is different from a second predefined
wavelength in a temperature range controlled by the temperature
adjustment means, and, when the temperature adjustment means is
driven, the second sub-substrate shifts a wavelength of other light
beam emitted from the second optical semiconductor device from the
second wavelength closer to the predefined wavelength.
[0014] (7) The optical transmitter module according to (3) may
further include sub-substrates, each disposed between a
corresponding optical semiconductor device of the optical
semiconductor devices and the submount in thermal communication
with the corresponding optical semiconductor devices and the
submount, configured to cause temperatures of at least two of the
optical semiconductor devices to be different from each other when
the temperature adjustment means is driven.
[0015] (8) In the optical transmitter module according to (7),
thicknesses of the sub-substrates may be substantially the
same.
[0016] (9) In the optical transmitter module according to (5) or
(6), thermal resistance of the first sub-substrate between the
submount and the first optical semiconductor device may be
different from thermal resistance of the second sub-substrate
between the submount and the second optical semiconductor
device.
[0017] (10) In the optical transmitter module according to any one
of (3) to (9), heat conductivity of a material forming the first
sub-substrate may be lower than heat conductivity of a material
forming the submount.
[0018] (11) In the optical transmitter module according to (1) or
(2), the first thermal resistor may be a first sub-substrate
directly mounted on the temperature adjustment means, the first
optical semiconductor device may be directly mounted on the first
sub-substrate, and, a second optical semiconductor device of the
optical semiconductor devices which is different from the first
optical semiconductor device may be directly mounted on the
temperature adjustment means.
[0019] (12) The optical transmitter module according to (1) or (2)
may further include a second sub-substrate, the first thermal
resistor may be a first sub-substrate directly mounted on the
temperature adjustment means, the first optical semiconductor
device may be directly mounted on the first sub-substrate, the
second optical semiconductor device may be directly mounted on the
temperature adjustment means, the second sub-substrate may be
directly mounted on the second sub-substrate, and, when the
temperature adjustment means is driven, the temperature adjustment
means may cause the temperatures of the first optical semiconductor
device and the second optical semiconductor device to be different
from each other.
[0020] (13) According to the present invention, there is provided
an optical module including the optical transmitter module
according to any one of the above (1) to (12); and an optical
receiver module.
[0021] (14) According to the present invention, there is provided
optical transmission equipment mounted with the optical module
according to the above (13).
[0022] (15) According to the present invention, there is provided a
method of manufacturing an optical transmitter module including
optical semiconductor devices, a temperature adjustment means for
collectively performing temperature adjustment on the optical
semiconductor devices, and a first thermal resistor that is
disposed between a first optical semiconductor device of the
optical semiconductor devices and the temperature adjustment means,
the method comprising: manufacturing the first optical
semiconductor device; measuring an output wavelength of a light
beam emitted from the first optical semiconductor device at a
reference temperature; comparing the output wavelength with a
reference wavelength range corresponding to the first optical
semiconductor device so as to obtain a wavelength difference; and
determining a material and dimensions of the first thermal resistor
on the basis of the wavelength difference.
[0023] According to the present invention, it is possible to
provide an optical transmitter module, an optical module, an
optical transmission equipment, and a method of manufacturing
thereof, capable of realizing low cost, miniaturization, and
adjustment of the temperature of each of a plurality of optical
semiconductor devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic diagram illustrating optical
transmission equipment and an optical module according to a first
embodiment of the present invention.
[0025] FIG. 2 is a diagram illustrating a plan view of the inside
of an optical transmitter module according to the first embodiment
of the present invention.
[0026] FIG. 3 is a cross sectional view of the optical transmitter
module according to the first embodiment of the present
invention.
[0027] FIG. 4 is a schematic diagram illustrating a part of the
optical transmitter module according to the first embodiment of the
present invention.
[0028] FIG. 5 is a diagram illustrating characteristics of a
thermal resistor for ceramic materials.
[0029] FIG. 6 is a schematic diagram illustrating a part of an
optical transmitter module according to a second embodiment of the
present invention.
[0030] FIG. 7 is a schematic diagram illustrating a part of an
optical transmitter module according to a third embodiment of the
present invention.
[0031] FIG. 8 is a schematic diagram illustrating a part of the
optical transmitter module according to the third embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings. A member having
the same configuration is given the same reference numeral
throughout the drawings for explaining the embodiments, and a
repeated description will not be made. The following drawings are
used to merely describe Examples of the embodiments, and a size of
each of the drawings does not necessarily match a scale described
in the Example.
First Embodiment
[0033] FIG. 1 is a schematic diagram illustrating an optical
transmission equipment 1 and an optical module 2 according to a
first embodiment of the present invention. The optical transmission
equipment 1 includes a printed circuit board 11 and ICs 12. The
optical transmission equipment 1 is, for example, a router or a
switch with large capacity. The optical transmission equipment 1
functions as, for example, a switch, and is disposed in a base
station or the like. The optical transmission equipment 1 is
mounted with a plurality of optical modules 2, acquires reception
data (reception electric signal) from the optical module 2,
determines what kind of data is to be transmitted to any one of the
optical modules by using the ICs 12 or the like, generates
transmission data (transmission electric signal), and delivers the
data to the corresponding optical module 2 via the printed circuit
board 11.
[0034] The optical module 2 is a transceiver having a function of
the optical transmitting and a function of the optical receiving.
The optical module 2 includes a printed circuit board 21, an
optical receiver module 23A which converts an optical signal which
is received via an optical fiber 3A into an electric signal, and an
optical transmitter module 23B which converts an electric signal
into an optical signal which is then transmitted to an optical
fiber 3B. The printed circuit board 21, and the optical receiver
module 23A and the optical transmitter module 23B are connected to
each other via flexible printed circuit boards 22A and 22B,
respectively. An electric signal from the optical receiver module
23A is transmitted to the printed circuit board 21 via the flexible
printed circuit board 22A, and an electric signal from the printed
circuit board 21 is transmitted to the optical transmitter module
23B via the flexible printed circuit board 22B. The optical module
2 and the optical transmission equipment 1 are connected to each
other via an electric port 5. The optical receiver module 23A and
the optical transmitter module 23B are electrically connected to
the printed circuit board 21, and respectively convert an optical
signal and an electric signal into an electric signal and an
optical signal.
[0035] A transmission system according to the present embodiment
includes two or more optical transmission equipments 1, two or more
optical modules 2, and one or more optical fibers 3 (for example,
the optical fibers 3A and 3B). Each optical transmission equipment
1 is connected to one or more optical modules 2. The optical
modules 2 respectively connected to two optical transmission
equipments 1 are connected to each other via the optical fibers 3.
Transmission data generated by one optical transmission equipment 1
is converted into an optical signal by the optical module 2
connected thereto, and the optical signal is transmitted to the
optical fibers 3. The optical signal transmitted on the optical
fibers 3 is received by the optical module 2 connected to the other
optical transmission equipment 1, the optical module 2 converts the
optical signal into an electric signal, and the electric signal is
transmitted to the other optical transmission equipment 1 as
reception data.
[0036] Here, a bit rate of electric signals transmitted from and
received by each optical module 2 is 100 Gbit/s. The optical
transmitter module 23B is a module based on a CFP system standard,
and performs dense wavelength division multiplexing (DWDM) in which
light at 25 Gbit/s (or 28 Gbit/s) is multiplexed with four
wavelengths at a wavelength interval of 20 nm, and is thus
transmitted at 100 Gbit/s.
[0037] FIG. 2 is a diagram illustrating a state in which the inside
of an optical transmitter module 30 according to the present
embodiment is viewed from the upper side. FIG. 3 is a sectional
view of the optical transmitter module 30 according to the present
embodiment. The optical transmitter module 30 according to the
present embodiment is the optical transmitter module 23B
illustrated in FIG. 1, for example.
[0038] The optical transmitter module 30 according to the present
embodiment includes a package 101, a submount 104 having a bottom
surface and a mounting surface, a Peltier element 110 disposed to
be in contact with the bottom surface of the submount 104, and
semiconductor lasers 200 (four semiconductor lasers in the present
embodiment) mounted on the mounting surface of the submount 104.
The optical transmitter module 30 further includes a collimator
lens 102 and a beam splitter 103 (optical de-multiplexer) mounted
on the mounting surface of the submount 104, wirings 105 (eight
wirings in the present embodiment), a feedthrough 106, an optical
multiplexer 107, a condenser lens 108, a receptacle terminal 109,
and light receiving elements 300 (four light receiving elements in
the present embodiment). The optical transmitter module 30 may be a
CAN type TOSA, and may be a box type optical transmitter module.
The submount 104 has a plate shape in which the bottom surface and
the mounting surface face each other, but is not limited thereto,
and may have, an L shape. Where the submount 104 has an L shape, a
surface in contact with a Peltier element is a bottom surface.
Where, a bottom surface does not face a mounting surface, but a
heat movement path is the same as where the bottom surface faces
the mounting surface. In other words, a large amount of heat moves
between the surface (mounting surface) on which the semiconductor
lasers are mounted and the surface (bottom surface) on which the
submount is in contact with the Peltier element.
[0039] In the optical transmitter module 30 according to the
present embodiment, the bottom surface of the submount 104 is
physically in contact with the Peltier element 110 and is thermally
connected thereto. The plurality of semiconductor lasers 200 are
thermally connected to the submount 104. Therefore, the Peltier
element 110 can be used to collectively adjust the temperatures of
the plurality of semiconductor lasers 200 via the submount 104.
Herein, where the optical transmitter module 30 is driven at a
predefined drive temperature, temperature adjustment is performed
by using the Peltier element 110 such that the submount 104 is
maintained at the predefined drive temperature (within a predefined
temperature range including the drive temperature).
[0040] Here, each of the semiconductor lasers 200 (four
semiconductor lasers in the present embodiment) is an EA-DFB laser
in which an electro absorption (EA) modulator and a distributed
feedback (DFB) laser are integrated on a semiconductor substrate in
a monolithic manner. Where the optical transmitter module 30 is
driven, the plurality of (four in the present embodiment)
semiconductor lasers 200 are required to respectively emit light
beams with predefined wavelengths which are different from each
other. The DFB laser is driven at a current of 70 mA and a voltage
of 1.3 V (power of 0.091 W), and the EA modulator is driven at a
current of 15 mA, a central bias of -0.7V, and a built-in voltage
of 0.95 V (power of 0.025 W). An optical output of the
semiconductor lasers 200 is 2 mW, and a heating value of a
termination resistor is as follows. A resistance value of the
termination resistor is 50.OMEGA.; a photocurrent in an ON state (a
light transmission state in which a high voltage is applied as a
bias voltage) in the EA modulator is 7.35 mA; a photocurrent in an
OFF state (light blocking state in which a low voltage is applied
as a bias voltage) is -14 mA; a photocurrent AC peak value is 3.325
mA; and power consumption is 0.00055 W. Therefore, in this case, a
total of heating values of the semiconductor lasers 200 is about
0.117 W.
[0041] Among the semiconductor lasers 200 (four semiconductor
lasers in the present embodiment), the semiconductor laser 200
located on the lower part in FIG. 2 is referred to as a first
semiconductor laser 200A, and the remaining three semiconductor
lasers 200 are referred to as second semiconductor lasers 200B. A
main feature of the optical transmitter module 30 according to the
present embodiment is that there is provided a first sub-substrate
(not illustrated) which is disposed between the first semiconductor
laser 200A and the Peltier element 110 and hinders transfer of heat
emitted from the first semiconductor laser 200A. Details of such a
configuration will be described later.
[0042] Each of the semiconductor lasers 200 (four semiconductor
lasers in the present embodiment) is electrically connected to the
feedthrough 106 via a plurality of wires 105A. Each of the light
receiving elements 300 (four light receiving elements in the
present embodiment) is electrically connected to the feedthrough
106 via a plurality of wires 105B. The plurality of semiconductor
lasers 200 are stored to be arranged side by side in the package
101, and each of the plurality of semiconductor lasers 200 emits
light L with a predefined wavelength. The light L emitted from each
of the plurality of semiconductor lasers 200 is emitted in the same
direction. For simplification, in FIGS. 2 and 3, a single wire 105A
and a single wire 105B are respectively illustrated as the
plurality of wires 105A and the plurality of wires 105B.
[0043] The light L emitted from each of the plurality of
semiconductor lasers 200 through space transmission inside the
package 101 passes through the collimator lens 102 provided in a
direction in which the light L is emitted, and is thus converted
into parallel light. As illustrated in FIGS. 2 and 3, the
collimator lens 102 may be a microlens array in which a plurality
of lenses are arranged side by side and are connected to each
other.
[0044] The light L converted into the parallel light is then
incident to the beam splitter 103 so as to branch into transmitted
light Lt and branch light Lb at a predetermined ratio. In other
words, the beam splitter 103 emits the transmitted light Lt in an
optical axis direction (the light emission direction of the
semiconductor laser 200), and emits the branch light Lb in a
direction perpendicular to the optical axis. Here, the branch light
Lb is emitted upward in FIG. 3 by the beam splitter 103.
[0045] A branch light beams (four branch light beams in the present
embodiment) Lb emitted upward by the beam splitter 103 are incident
to a light reception surface 301 of each of the light receiving
elements 300 (four light receiving elements in the present
embodiment). As illustrated in FIG. 3, each of the plurality of
light receiving elements 300 is disposed on the beam splitter 103,
and the light reception surface 301 of each of the plurality of
light receiving elements 300 faces the beam splitter 103. Here, the
light receiving element 300 is, for example, a photodiode. The
light receiving element 300 monitors an optical output of the
semiconductor laser 200. The optical output of the semiconductor
laser 200 is controlled to be constant on the basis of a monitoring
result.
[0046] The transmitted light Lt which is transmitted through the
beam splitter 103 as a part of the light emitted from the
semiconductor laser 200 is incident to the optical multiplexer 107
which multiplexes light, and then the light is multiplexed in the
optical multiplexer 107 so as to be output as light Lout which is
transmitted to the outside. The light Lout emitted from the optical
multiplexer 107 is then collected in the condenser lens 108, and is
incident to the receptacle terminal 109 which is connected to a
receptor. The receptacle terminal 109 is optically connected to an
external optical fiber (not illustrated), and light output from the
receptacle terminal 109 is transmitted through the optical
fiber.
[0047] The inside of the package 101 of the optical transmitter
module 30 may be in a vacuum state, and may be filled with an inert
gas (for example, a nitrogen gas), a dry air, or the like. Where
the inside of the package 101 is filled with an inert gas as
mentioned above, the reliability of the optical transmitter module
30 can be increased.
[0048] FIG. 4 is a schematic diagram illustrating a part of the
optical transmitter module 30 according to the present embodiment.
In FIG. 4, the semiconductor lasers 200 (four semiconductor lasers
in the present embodiment) arranged in a first direction (a
horizontal direction in FIG. 4) are mounted on the mounting surface
of the submount 104. Among the four semiconductor lasers 200, the
(three) second semiconductor lasers 200B are directly mounted on
the mounting surface of the submount 104, whereas the first
semiconductor laser 200A is mounted on the mounting surface of the
submount 104 via a first sub-substrate 210A. In other words, the
first sub-substrate 210A is disposed between the first
semiconductor laser 200A and the submount 104, and is thermally
connected to both of the two.
[0049] In the present specification, a case where the semiconductor
lasers 200 are mounted on the submount 104 includes a case where
the semiconductor laser 200 is physically in contact with the
mounting surface of the submount 104 and is directly mounted
thereon, and a case where a thermal resistor is disposed to be
physically in contact with the mounting surface of the submount
104, and the semiconductor laser 200 is physically in contact with
the thermal resistor so as to be mounted, that is, indirectly
mounted.
[0050] Wiring patterns 116 connected to a plurality of electrodes
of the mounted semiconductor lasers 200 are formed on the mounting
surface of the submount 104. The plurality of wiring patterns 116
are respectively connected to the plurality of electrodes via wires
115. The semiconductor laser 200 includes an EA modulator portion
and a DFB laser portion. A pair of EA electrodes of the EA
modulator portion are electrically connected to a pair of wiring
patterns 116A and 116B via a pair of wires 115A and 115B,
respectively. One of a pair of DFB electrodes of the DFB laser
portion is electrically connected to a wiring pattern 116C via a
wire 115C. The other electrode is disposed on the bottom surface
side of the semiconductor laser 200, and is electrically connected
to a corresponding electrode pattern 116D. The other DFB electrode
of the first semiconductor laser 200A is electrically connected to
the corresponding electrode pattern 116D through a via hole (not
illustrated) provided in the first sub-substrate 210A. However, the
connection there between is not limited thereto, and may be
realized, for example, according to a method of metalizing a side
surface of the first sub-substrate 210A. In the present embodiment,
a material of the submount is aluminum nitride.
[0051] Here, the first sub-substrate 210A is a thermal resistor
(first thermal resistor) hindering transfer of heat emitted from
the first semiconductor laser 200A when the Peltier element 110 is
driven. Thermal connection between each of the semiconductor lasers
200 and the submount 104 is sufficiently ensured through heat
conduction. Therefore, where the first sub-substrate 210A (first
thermal resistor) is disposed between the first semiconductor laser
200A and the submount 104, the first sub-substrate 210A functions
as a thermal resistor which has high thermal resistance and reduces
heat dissipation.
[0052] Where the optical transmitter module 30 is driven, the
submount 104 is controlled at a predefined drive temperature (a
predefined temperature range including the drive temperature) by
using the Peltier element 110. Each of the plurality of
semiconductor lasers 200 is required to emit a light beam with a
predefined wavelength at the predefined drive temperature.
Therefore, at a reference temperature, each output wavelength of
each light beam emitted from each of the semiconductor lasers 200
is required to fall within a reference wavelength range. Here, for
simplification, it is assumed that a drive temperature is the same
as a reference temperature as 50.degree. C.
[0053] In the embodiment, an output wavelength of a light beam
emitted from the first semiconductor laser 200A at the reference
temperature does not fall within the corresponding reference
wavelength range, and is shorter than the wavelength range. In
contrast, an output wavelength of each light beam emitted from each
of the three second semiconductor lasers 200B at the reference
temperature falls within the corresponding reference wavelength
range.
[0054] Each second semiconductor laser 200B is directly mounted on
the mounting surface of the submount 104, and, where the submount
104 is maintained at the drive temperature by using the Peltier
element 110, each second semiconductor laser 200B is maintained at
the drive temperature (and the predefined temperature range).
Therefore, each second semiconductor laser 200B can emit a light
beam with the predefined wavelength (the predefined wavelength
range including the wavelength) at the drive temperature.
[0055] In contrast, if the first sub-substrate 210A is not
disposed, and the first semiconductor laser 200A is directly
mounted on the mounting surface of the submount 104, the first
semiconductor laser 200A emits a light beam with a first wavelength
which is different from the predefined wavelength (the predefined
wavelength range including the wavelength) at the drive
temperature. However, in the optical transmitter module 30
according to the present embodiment, the first sub-substrate 210A
is disposed between the first semiconductor laser 200A and the
submount 104. Thus, the first sub-substrate 210A functions as a
thermal resistor, and the semiconductor laser 200A is in a state in
which heat dissipation is reduced compared with the semiconductor
lasers 200B. Specifically, outflow paths of heat from the
semiconductor laser 200 which is a heat generation body includes a
path along which heat is transferred to the submount 104 via the
mounting surface, a path along which heat is transferred to the
submount 104 via the plurality of wires 115, and a path along which
heat is emitted through heat radiation where the package inside is
filled with a gas. Among the paths, an amount of heat based on heat
radiation to the ambient gas is sufficiently smaller than an amount
of heat based on heat conduction to the submount 104, and thus a
large amount of heat from the semiconductor lasers is transferred
to the submount 104. The submount 104 is maintained at the drive
temperature by using the Peltier element 110, and the temperature
of the second semiconductor laser 200B directly mounted on the
submount 104 is substantially the same as the temperature of the
mounting surface of the submount. Strictly speaking, the
temperature of the second semiconductor laser 200B is higher by a
thermal resistance of the contact portion (generally, connection
using soldering) between the submount 104 and the second
semiconductor laser 200B, but, herein, for simplification of
description, the contact resistance is ignored, and the temperature
of the mounting surface of the submount 104 is assumed to be the
same as the temperature of the second semiconductor laser 200B. In
contrast, the semiconductor laser 200A is physically and thermally
connected to the submount 104 via the first sub-substrate 210A
which is a thermal resistor. The first sub-substrate 210A is a
thermal resistor, and thus reduces heat conduction to the submount
104 of heat generated from the semiconductor laser 200A (reduction
in heat dissipation). As a result, a thermal equilibrium state
occurs in a state in which the temperature of the semiconductor
laser 200A is substantially the same as that of the connection
surface with the first sub-substrate 210A (as described above, the
contact resistance is ignored), and the temperature of the
connection surface between the first sub-substrate 210A and the
semiconductor laser 200A is higher than the temperature of the
connection surface with the submount 104.
[0056] Therefore, the temperature of the first semiconductor laser
200A is higher than the drive temperature, and an output wavelength
of a light beam emitted from the first semiconductor laser 200A is
shifted to a longer wavelength side than an output wavelength where
the first semiconductor laser 200A is driven at the drive
temperature. The first sub-substrate 210A is formed by selecting an
appropriate material or dimension, and thus an output wavelength of
a light beam emitted from the first semiconductor laser 200A can be
made come closer to the predefined wavelength than the first
wavelength. More preferably, an output wavelength of a light output
from the first semiconductor laser 200A can be made the predefined
wavelength. For simplification of description, the description has
been made assuming that the temperature of the semiconductor laser
200 does not have a distribution. Strictly, a heat distribution is
present even in the inside of the semiconductor laser 200, but,
herein, has not been described in order to describe the effect of
the first sub-substrate 210A.
[0057] Herein, a reference temperature and a drive temperature are
the same as each other, but are not limited thereto. An output
wavelength of a light beam emitted from the semiconductor laser 200
depends on a temperature. Therefore, a predefined wavelength
required for each semiconductor laser 200 at a drive temperature is
determined depending on a reference wavelength range corresponding
to each semiconductor laser 200 at a reference temperature, and a
temperature difference between a drive temperature and a reference
temperature.
[0058] FIG. 5 is a diagram illustrating characteristics of a
thermal resistor for ceramic materials. Here, it is assumed that,
as dimensions of the first sub-substrate 210A, a width is 300
.mu.m, a length is 600 .mu.m, and a height is 100 .mu.m. Where a
thermal resistor is formed according to such dimensions by using
materials illustrated in FIG. 5, heat conductivity (W/mK) of the
materials, a temperature difference (K) caused by the thermal
resistor, and a difference in an output wavelength of a light beam
emitted from the semiconductor laser 200 are illustrated.
[0059] A method of manufacturing the first sub-substrate 210A of
the optical transmitter module 30 according to the present
embodiment is as follows. The first semiconductor laser 200A is
manufactured according to a well-known method. After the first
semiconductor laser 200A is manufactured, an output wavelength of a
light beam emitted from the first semiconductor laser 200A is
measured at a reference temperature. The measured output wavelength
is compared with a reference wavelength range corresponding to the
first semiconductor laser 200A such that a wavelength difference is
obtained. Specifically, a wavelength difference between the
measured output wavelength and a central value of the reference
wavelength range corresponding to the first semiconductor laser
200A is computed. Where a reference temperature is the same as the
drive temperature, a material and dimensions of the first
sub-substrate 210A are determined according to the wavelength
difference. Where the first sub-substrate 210A is formed according
to the dimensions illustrated in FIG. 5, a temperature difference
for complementing the wavelength difference may be calculated, and
a material or dimensions capable of causing the temperature
difference may be determined. Where the wavelength difference is
0.16 nm, the first sub-substrate 210A is preferably formed by using
alumina (Al.sub.2O.sub.3). In DWDM based on the CFP system
standard, since a wavelength difference between output wavelengths
adjacent to each other is about 4.5 nm, the first sub-substrate
210A is formed by using the representative ceramic materials
illustrated in FIG. 5, and thus an output wavelength of a light
beam emitted from the first semiconductor laser 200A can be made
sufficiently close to a predefined wavelength. Where a reference
temperature is different from a drive temperature, a temperature at
which the first semiconductor laser 200A can emit a light beam with
a predefined wavelength may be calculated according to a wavelength
difference on the basis of the drive temperature of the Peltier
element 110, and a material or dimensions capable of causing a
temperature difference may be determined. Generally, a material
having high heat dissipation (a material having high heat
conductivity, and, for example, aluminum nitride) is used for the
submount 104. In contrast, the first sub-substrate 210A is formed
by using a material having lower heat conductivity than that of the
submount, and dimensions thereof are smaller than those of the
submount, so that thermal resistance can be increased. Thus, a
temperature difference between the first semiconductor laser 200A
and the mounting surface of the submount 104 can be increased. The
submount 104 and the first sub-substrate 210A may be made of the
same material, but different materials are preferably used in order
to obtain a greater temperature difference.
[0060] The optical transmitter module 30 according to the present
embodiment includes the first sub-substrate 210A. If the first
semiconductor laser 200A is directly mounted on the mounting
surface of the submount 104 without using the first sub-substrate
210A, the first semiconductor laser 200A cannot be used at a drive
temperature. Therefore, the first semiconductor laser 200A is
discarded, and thus a yield is reduced. Since the first
sub-substrate 210A is disposed on the submount 104, the first
semiconductor laser 200A can be driven at a temperature (higher
than a drive temperature) which is different from the drive
temperature, and thus the first semiconductor laser 200A can be
used for the optical transmitter module 30. Since the thermal
resistor is disposed, an effective drive temperature of the
semiconductor laser can be adjusted instead of performing
temperature adjustment by using an individual Peltier element, and
thus it is possible to adjust an available wavelength range of the
semiconductor laser. The semiconductor lasers can be driven by
using a single Peltier element, and thus it is possible to realize
miniaturization and low power consumption. A wavelength range
specification of the semiconductor laser can be expanded, and thus
a yield of the semiconductor laser can be improved. The first
sub-substrate 210A (thermal resistor) used in the present
embodiment does not generate heat. For example, even where a heater
is used instead of the first sub-substrate 210A, a wavelength range
can be adjusted. However, in a case of the heater, a wiring, a
power source, and the like for driving the heater are necessary,
and thus it is hard to provide an optical transmitter module
satisfying miniaturization and low cost. According to the present
invention, it is possible to individually adjust a wavelength of
the semiconductor laser by using a simple ceramic substrate or the
like.
Second Embodiment
[0061] FIG. 6 is a schematic diagram illustrating a part of an
optical transmitter module 30 according to a second embodiment of
the present invention. Apart of the optical transmitter module 30
illustrated in FIG. 6 corresponds to a part of the optical
transmitter module 30 according to the first embodiment illustrated
in FIG. 4. The optical transmitter module 30 according to the
present embodiment has the same structure as that in the first
embodiment except for configurations of semiconductor lasers 200
(four semiconductor lasers in the present embodiment) and
sub-substrates 210 (four sub-substrates in the present embodiment)
(thermal resistors) disposed on the mounting surface of the
submount 104. The four semiconductor lasers 200 mounted on the
submount 104 according to the present embodiment are a first
semiconductor laser 200A, a second semiconductor laser 200B, a
third semiconductor laser 200C, and a fourth semiconductor laser
200D, and the sub-substrate 210 is disposed between each
semiconductor laser 200 and the submount 104. In other words, a
first sub-substrate 210A, a second sub-substrate 210B, a third
sub-substrate 210C, and a fourth sub-substrate 210D are
respectively disposed between the submount 104 and the four
semiconductor lasers 200. Herein, the sub-substrates 210 (four in
the present embodiment) have the substantially same dimensions.
Regarding materials, materials of the first sub-substrate 210A and
the third sub-substrate 210C are the same as each other, and
materials of the second sub-substrate 210B and the fourth
sub-substrate 210D are the same as each other.
[0062] The second semiconductor laser 200B is different from the
first semiconductor laser 200A, and preferably emits a light beam
with a wavelength which is different from an output wavelength of a
light beam emitted from the first semiconductor laser 200A when the
optical transmitter module 30 is driven. In the same manner as the
first semiconductor laser 200A, an output wavelength of a light
beam emitted from the second semiconductor laser 200B at a
reference temperature does not fall within a corresponding
reference wavelength range, and is shorter than the wavelength
range. The second sub-substrate 210B is a thermal resistor (second
thermal resistor) for causing a temperature difference from the
mounting surface of the submount 104 in the second semiconductor
laser 200B when the Peltier element 110 is driven. In the present
embodiment, the second semiconductor laser 200B is the same for the
third semiconductor laser 200C and the fourth semiconductor laser
200D, and the second sub-substrate 210B is the same for the third
sub-substrate 210C and the fourth sub-substrate 210D.
[0063] The four semiconductor lasers 200 are respectively
maintained at temperatures higher than a drive temperature at which
the submount 104 is maintained by the corresponding sub-substrates
210 when the Peltier element 110 is driven. Each sub-substrate 210
is formed by selecting an appropriate material or dimension, and
thus an output wavelength of a light beam emitted from the first
semiconductor laser 200 can be made to come closer to a predefined
wavelength than an output wavelength at a drive temperature. An
output wavelength of the second semiconductor laser 200B at the
drive temperature is a second wavelength. More preferably, an
output wavelength of a light output from each semiconductor laser
200 can be made the predefined wavelength.
[0064] A material or dimensions of each of the sub-substrates 210
may be selected according to characteristics of the corresponding
semiconductor laser 200, but, among the semiconductor lasers 200
(four in the present embodiment), materials or/and dimensions of
two sub-substrates 210 disposed under at least two semiconductor
lasers 200 are preferably different from each other. If materials
and dimensions of the sub-substrates 210 (four sub-substrates in
the present embodiment) are the same as each other, the
significance of disposing the sub-substrates 210 is reduced, and
thus the submount 104 may be maintained at a higher temperature by
using the Peltier element 110 instead of disposing the
sub-substrates 210.
[0065] The four sub-substrates 210 are respectively disposed
between all of the four semiconductor lasers 200 mounted on the
submount 104 according to the present embodiment and the submount
104. Here, the four sub-substrates 210 are manufactured according
to common dimensions. At least thicknesses of all of the four
sub-substrates 210 are preferably substantially the same as each
other. Where the optical transmitter module 30 has such a
configuration, heights of light emission locations (light emission
central points) in the four semiconductor lasers 200 manufactured
to have a common structure are substantially the same as each
other. In the optical transmitter module 30 according to the
present embodiment, a microlens array having four collimator lenses
102 can be used, and thus an optical axis can be easily adjusted by
using a plurality of lenses.
[0066] In the present embodiment, unlike the first embodiment, a
plurality of electrodes of the semiconductor lasers 200 and a
plurality of electrode patterns 116 formed on the mounting surface
of the submount 104 are respectively electrically connected to each
other via wires 115 (four wires in the present embodiment). Unlike
the first embodiment, a via hole is not provided in the
sub-substrate 210, and thus a greater temperature difference using
large thermal resistance can be realized. A pair of EA electrodes
of the EA modulator portion of the semiconductor laser 200 are
electrically connected to a pair of wiring patterns 116A and 116B
via a pair of wires 115A and 115B, respectively. A pair of laser
electrodes of the DFB laser portion of the semiconductor laser 200
are electrically connected to the pair of wiring patterns 116C and
116D via the pair of wires 115C and 115D.
[0067] In the present embodiment, the four sub-substrates 210 are
respectively disposed between the four semiconductor lasers 200 and
the mounting surface of the submount 104. Since the four
sub-substrates 210 are disposed, an optical axis is easily adjusted
by using a plurality of lenses, but the present invention is not
limited thereto. Unlike the first embodiment, the first
sub-substrate 210A and the second sub-substrate 210B are
respectively disposed for the first semiconductor laser 200A and
the second semiconductor laser 200B, so that two sub-substrates 210
are disposed according to the respective two semiconductor lasers
200, and thus the optical transmitter module 30 can be configured
according to characteristics of the first semiconductor laser 200A
and the second semiconductor laser 200B.
Third Embodiment
[0068] FIG. 7 is a schematic diagram illustrating a part of an
optical transmitter module 30 according to a third embodiment of
the present invention. A part of the optical transmitter module 30
illustrated in FIG. 7 corresponds to a part of the optical
transmitter module 30 according to the first embodiment illustrated
in FIG. 4. The optical transmitter module 30 according to the
present embodiment has the same structure as that in the first
embodiment except that the submount 104 is not provided, and
semiconductor lasers 200 are mounted on the Peltier element
110.
[0069] As illustrated in FIG. 7, the optical transmitter module 30
according to the present embodiment does not include the submount
104, and semiconductor lasers 200 are mounted on the Peltier
element 110. The Peltier element 110 has a mounting surface, and a
first sub-substrate 210A is disposed between the first
semiconductor laser 200A and the Peltier element 110. Among the
semiconductor lasers 200, three semiconductor lasers 200 other than
the first semiconductor laser 200A are second semiconductor lasers
200B, and the three second semiconductor lasers 200B are directly
mounted on the Peltier element 110.
[0070] Wiring patterns 116 electrically connected to the mounted
semiconductor lasers 200 are formed on the mounting surface of the
Peltier element 110 according to the present embodiment. The wiring
patterns 116 connected to the first semiconductor laser 200A are
the same as the wiring patterns 116 (refer to FIG. 6) according to
the second embodiment formed on the mounting surface of the
submount 104, and the wiring patterns 116 respectively connected to
the three second semiconductor lasers 200B are the same as the
wiring patterns 116 (refer to FIG. 4) according to the first
embodiment formed on the mounting surface of the submount 104.
Fourth Embodiment
[0071] FIG. 8 is a schematic diagram illustrating a part of an
optical transmitter module 30 according to a fourth embodiment of
the present invention. Apart of the optical transmitter module 30
illustrated in FIG. 8 corresponds to a part of the optical
transmitter module 30 according to the second embodiment
illustrated in FIG. 6. The optical transmitter module 30 according
to the present embodiment includes a submounts 104 on which
semiconductor lasers 200 are respectively mounted. Here, a first
submount 104A disposed between the first semiconductor laser 200A
and the Peltier element 110 is a first thermal resistor, and a
second submount 104B disposed between the second semiconductor
laser 200B and the Peltier element 110 is a second thermal
resistor. This is also the same for a third submount 104C and a
fourth submount 104D.
[0072] Wiring patterns 116 electrically connected to the
semiconductor lasers 200 are formed on mounting surfaces of the
submounts 104 according to the present embodiment, but the
respective wiring patterns 116 are the same as the wiring patterns
116 (refer to FIG. 4) according to the first embodiment formed on
the mounting surface of the submount 104.
[0073] As mentioned above, the submount, the optical transmitter
module, and the optical module, and the control method therefor
according to the embodiments of the present invention have been
described. In the embodiments, an optical semiconductor device is a
semiconductor laser, but is not limited thereto, and the
embodiments are widely applicable to other optical semiconductor
devices such as a photodiode (PD) device. In the embodiments, a
semiconductor laser is an EA-DFB laser, but is not limited thereto,
and the present invention is widely applicable to other
semiconductor lasers such as a CW light source and a
direct-modulation semiconductor laser. The optical transmitter
module according to the embodiments includes four semiconductor
lasers of the CFP system, but is not limited thereto, and the
optical transmitter module may include, for example, eight
semiconductor lasers. In the embodiments, a single Peltier element
is used as a single piece of temperature adjustment means, but this
is only an example, and other temperature adjustment mechanisms may
be used. The present invention is widely applicable to an optical
transmitter module achieving the effects of the present
invention.
[0074] While there have been described what are at present
considered to be certain embodiments of the invention, it will be
understood that various modifications may be made thereto, and it
is intended that the appended claims cover all such modifications
as fall within the true spirit and scope of the invention.
* * * * *